The various curves correspond to the available preset configurations (see the Goodman cheatsheet [1] or the Goodman Overview [2])
Here we present plots for various central wavelengths in Littrow configuration
Links
[1] http://www.ctio.noirlab.edu/soar/sites/default/files/GOODMAN/Images/New_Goodman_Cheat_Sheet.pdf
[2] http://www.ctio.noirlab.edu/soar/content/goodman-spectrograph-overview